Metal-aggregate product



United States Patent ()fiice 3,055,763 Patented Sept. 25, 1962 3,055,763METAL-AGGREGATE PRODUCT Jack R. Kreigh and James Keith Gibson, both ofR0. Box 445, La Salle, Ill. No Drawing. Filed July 10, 1958, Ser. No.747,600 5 Claims. (Cl. res-41) This invention relates to improvements ina product comprising metal and an aggregate, the product beingcharacterized in that the metal has a lower melting point than theaggregate and carries the aggregate as discrete pieces embedded more orless uniformly in a matrix of the metal.

This unique product comprising the present invention is composed of ametal or metal alloy in which is embedded, more or less uniformly, anaggregate so selected as to impart desired characteristics to theresulting mass, the metallic content of the mass being in the continuousor external phase.

By the proper selection of the aggregate and percentages thereof variouscharacteristics may be imparted to the resulting mass, that is, itsspecific gravity may be varied; its strength-to-Weight ratio may bevaried; its handling ability may be varied, that is, it may be soconstituted as to be readily sawn or received nails or screws or otherfastening means; its heat or electrical conductivity may be varied andin general the mass may be made to differ materially from the metal ormetal alloy in its unmixed state.

Although substantially any metal or metal alloy may be employed in thisinvention, the lower melting point metals, that is, those having amelting point of about 700 C. or below, or alloys thereof, such as,lead, zinc, tin, aluminum and magnesium appear to oifer the greatestpossibilities, and we prefer aluminum and magnesium or alloys thereofsince extremely light-weight products and products having highstrength-to-weight ratios may be made.

Aggregates of many types may be employed limited generally by thequalification that they have a melting point above the melting point ofthe metal with which they are used, and will not appreciably dissolve ordisintegrate when mixed with the molten metal, as will be hereinafterdescribed. Preferably the aggregate comprises a nonmetallic mineralmaterial. Thus, for aluminum or magnesium or the alloys thereof, mineralaggregates, such as vermiculite (Zonolite), perlite, groundrefractories, fired clay pellets or the like have been successfullyused. Aggregates such as those enumerated may also be used with othermetals since they do not melt or disintegrate at the molten temperaturesof the metals contemplated.

In incorporating the aggregate in the metal, the selected metal may bemelted in a suitable receptacle and the aggregate may be introducedtherein and, with or without the addition of heat, the mass may bevigorously mixed to uniformly disperse the aggregate particles in themetal mass. While the mixing is continued the mass may be permitted tocool until the metal reaches a viscous state at which time the mixing isdiscontinued and the mass permitted to solidify with the aggregateembedded therein. When the metal reaches the viscous state mentionedherein before, the aggregate particles will not tend to stratify in themetal mass. If desired, before the mass solidifies, and while it isstill in a relatively flowable, although viscous, condition, it may bepoured into a suitable mold wherein it is permitted to solidify. Or, ifdesired, before the mass completely solidifies, and while stratificationof the aggregate is inhibited, it may be passed through a conventionalextrusion die to form desired extruded shapes.

The resulting mass is particularly characterized in that the aggregateparticles are substantially unmelted or unfluxed and exist in the metalmatrix as substantially uniformly distributed discrete particles and arerelated to the metal mass not unlike the aggregate in the usualcement-concrete mixture.

As an example of control which may be exercised over the metal-aggregateproduct by the proper selection and proper proportions of aggregate tometal, 2 parts of vermiculite was mixed with 1 part of an aluminumalloy, by volume. During the mixing operation the metal originallyintroduced at 1275 F. cooled to about 1070 F. at which time the metalwas sufliciently viscous as to prevent segregation or stratification.The resulting mass had a specific gravity of less than 1, that is, itwould float on water. The aluminum alloy remained in the continuous orexternal phase. The product was not a sponge material, that is, itcontained no voids, as such, but appeared as a "virtual solid comprisingthe metal and the uniformly embedded vermiculite particles.

As another example of control which may be exercised over the metalaggregate product by the proper selection and proper proportions ofaggregate to metal, 1 /2 parts of fired clay pellets was mixed with 1part of an aluminum-magnesium alloy, by volume. During the mixingoperation the metal originally introduced at 1325' F. cooled to about1070 F., at which time the metal was sufficiently viscous as to preventsegregation or Stratification. The resulting mass had a specific gravityof more than 1 but less than the specific gravity of the alloy used. Thealloy remained in the continuous or external phase.

It is desirable that the aggregate be in such condition as not toinhibit the wetting of its surfaces by the metal. Hence, it is desirablethat the aggregate be dry and carry no surface moisture or oil surfacefilm.

The product comprising the present invention, in general, has use wherea relatively light-weight strong material is desired; where asubstantially fireproof, rustproof, rotproof, vermin and rodentproofmaterial is desired without the necessity of painting or coating. Thematerial has greater heat and sound insulation than the unmixed metalcomprising the matrix, and can be used Where a floating material isdesired and where deterioration is a problem. The material may be usedin making castings of light weight, the aggregate being employed as afiller for the more expensive metal. It may also be used as a relativelyinexpensive, light-weight core material for fire doors or the like. Itcan be conveniently handled, since it may be readily sawn and willretain nails or other fastening means.

We claim as our invention:

1. A light-weight solid product having a high strengthto-weight ratiowhich can be readily sawn comprising a metallic matrix and mineralaggregate in particle form embedded and substantially uniformlydispersed in said matrix, said metal being of the class consisting ofaluminum and magnesium and alloys thereof, said aggregate being selectedfrom the group consisting of vermiculite and fired clay pellets andhaving a melting point above the melting point of the metal and being ofrelatively light weight and substantially stable in the presence of saidmetal when the latter is in molten condition, said aggregate being inmajor proportion by volume and substantially uniformly distributed indiscrete pieces throughout said metallic matrix, the latter being in theexternal continuous phase.

2. The composition of claim 1 wherein the metal is aluminum.

3. The composition of claim 1 wherein the metal is magnesium.

3 4 5. The composition of claim 1 wherein the aggregate 2,763,519Thomson Sept. 18, 1956 is fired clay pellets. 2,805,473 Handwerk Sept.10, 1957 2,929,133 Hughes Mar. 22, 1960 References Cited in the file ofthis patent 2,947,068 Nachtman Aug. 2, 1960 UNITED STATES PATENTS 52,951,280 Spokes p 1960 934,412 Marius Sept. 14, 1909 FOREIGN PATENTS2,568,157 Lepp Feb. 12, 1949 456,467 Canada May 3, 1949

1. A LIGHT-WEIGHT SOLID PRODUCT HAVING A HIGH STRENGTHTO-WEIGHT RATIOWHICH CAN BE READILY SAWN COMPRISING A METALLIC MATRIX AND MINERALAGGREGATE IN PARTICLE FORM EMBEDDED AND SUBSTANTIALLY UNIFORMLYDISPERSED IN SAID MATRIX, SAID METAL BEING OF THE CLASS CONSISTING OFALUMINUM AND MAGANESIUM AND ALLOYS THEREOF, SAID AGGREGATE BEINGSELECTED FROM THE GROUP CONSISTING OF VERMICULITE AND FIRED CLAY PELLETSAND HAVING A MELTING POINT ABOVE WEIGHT AND SUBSTANTIALLY STABLE IN THEPRESENCE OF SAID METAL WHEN THE LATTER IS IN MOLTEN CONDITION, SAIDAGGREGATE BEING IN MAJOR PROPORTION BY VOLUME AND SUBSTANTIALLY UNIFORMYDISTRBUTED IN DISCREAT PIECES THROUGHTOUT SAID METALLIC MATRIX, THELATTER BEING IN THE EXTERNAL CONTINUOUS PHASE.